1. Field of the Invention
The present invention relates to a device for displaying both critical information and non-critical information.
2. Brief Discussion of the Related Art
The critical information is information that it is essential for an aircraft pilot to know and that, if erroneous, could lead directly to the loss of the aircraft. The main items of critical information are speed and altitude. That is why a device for displaying critical data is thus itself an element that is critical, such that use thereof on board an aircraft must be preceded by a qualification or certification procedure including stringent tests seeking to demonstrate the robustness, the accuracy, and the reliability of the display device under all circumstances. The design and the fabrication of such a display device are therefore expensive.
In order to improve crew comfort, it is known to display information in the cockpit that is useful, but without being critical. By way of example, this information may comprise outside and inside temperatures, time data, data relating to the operation of certain elements of the aircraft, navigation data, and other information of this type. The device for displaying this information may itself be a non-critical display device or it may be a critical display device.
Proposals are now being made also to display non-critical information that is relatively complex such as map information or more particularly images known as terrain rendering that provide a three-dimensional representation of the zone of the earth's surface over which the aircraft is flying. Displaying terrain rendering images requires two databases, namely: an altitude database containing the altitudes of various points of a territory, which altitudes are determined as a function of a mesh of the territory, together with a photographic database containing aerial photographs of zones surrounding the various points of the territory and using the same mesh. Terrain rendering images are produced by fitting the photographs to the relief extracted from the altitude database. That operation is particularly greedy in terms of calculation and demands large amounts of computer resources, particularly when it is desired to have the images displayed in real time with a refresh rate lying in the range 25 hertz (Hz) to 100 Hz.
Critical display devices do not have sufficient power to perform such calculations, and the amount of development that would be needed to design a critical display device suitable for displaying such information is so great, in particular in terms of qualification testing, that it is considered that providing a critical display device of that kind is completely unrealistic.
It is therefore necessary to have recourse to a non-critical consumer display device that is sold in sufficient volume to justify development costs. However, even there, it would be too expensive to carry out qualification testing on such display devices.
Simultaneously displaying both critical information and non-critical information thus requires the use of both a critical display device and of a non-critical display device, such that the critical and non-critical information is displayed on two different screens. Since non-critical information is generally presented in a manner that is visually more attractive than critical information, there is a risk of the pilot's attention being monopolized by the non-critical information to such an extent that the pilot does not monitor the critical information with all the necessary attention, particularly since the terrain rendering images may, from the point of view of the information they convey, replace in part a raw display of altitude.